symbols: Build in Docker

Created by: chrismwendt

Build symbols in Docker rather than outside of Docker then copying it in.

This eliminates the need for cross compilation and the resulting problems such as some tree-sitter grammars needing g++ but there's no musl-g++ that I could find.

I think this will fix the broken #33689 (which was reverted in https://github.com/sourcegraph/sourcegraph/pull/34316).

More details in Slack.

Test plan

main-dry-run: https://buildkite.com/sourcegraph/sourcegraph/builds?branch=main-dry-run%2Fsymbols-build-in-docker

Ran locally, container at least starts.